Microscope objective



SEARCH RUUNI 0R 2,694,362 VWOSYQH July 7, 1953 G. RAvlzzA E-r/u.

MICROSCOPE OBJECTIVE 2 Sheets-Sheet 1 Filed July 5, 1951 (H H) (1L) 1NVEN TORS July 7, 1`953 G. RAvlzzA Erm. 2,644,362

MICROSCOPE OBJECTIVE Filed July 5. 1951 2 Sheets-Sheet 2 INVENTORS,

Patented July 7, 1953 MICROSCOPE OBJECTIVE Gottfried Ravizza, Wetzlar,Karl Keiner, Berghausen, and Walter Klein, Dutenhofen, Germany,assignors to Ernst Leitz, G. m. b. H., a

corporation of Germany Application July 5, 1951, Serial No. 235,132 InGermany July 26, 1950 6 Claims.

This invention relates to improvements in microscope objectives. Mostmicroscope objectives have a considerable curvature of the image fieldand the compensating effect of the ocular is utilized to overcome thisdefect. However, the problem of leveling the image field by itself is animportant problem and many attempts have been made to solve it. Onearrangement in particular has become known, namely the leveling of theimage field curvature by the use of so called thick menlsci. A thickmeniscus is a lens having a dispersing surface which is more stronglycurved than its converging surface and the thickness of the lens isgreater than one half the radius of the dispersing surface. It has arelatively great negative or also positive focal length according to itsthickness. Sometimes a meniscus may consist of cemented single lenses.It is also known that such a meniscus has a Petzval sum which is zero orless than zero. When the meniscus is used as a front lens it is subjectto considerable astigmatism.

The British Patent 506,321, May 25, 1939, or U. S. Patent 2,206,155,dated July 2, 1940, discloses an objective in which the astigmatism of athick meniscus which is curved toward the object and serves as a frontlens is eliminated by means of a second thick meniscus which is the lastlens element toward the ocular side and which is convex toward theobject. The second thick meniscus therefore increases the negative valueof the Petzval sum.

The manufacture of a thick meniscus is difficult because of its strongcurvatures and the object of this `invention is therefore to provide forcorrection for astigmatism and at the same time avoid the use of thesecond thick meniscus.

The invention is embodied in a microscope objective in which a thickmeniscus serves as the front lens and is corrected for astigmatism bybeing followed, first, by a dispersing cemented surface within aconverging lens member, the center of curvature of the cemented surfacebeing on the object side, and, second, by a negative lens arranged onthe image side thereof.

Such a combination of lens elements arranged in accordance with theinvention provides a steady opposing effect against astigmatism of thethick meniscus and serves also to eliminate other faults of the image bymeans of further converging lenses of known types.

The accompanying drawings Figs. 1 through 5 illustrate in axial sectionscalculated examples containing the date set forth in the tables ofvalues appearing hereinafter in the description 2 of each of the figuresin the drawings and also included in the claims which are to be readaccordingly. In these tables the radii of curvatures, thelens-thicknesses, the axial distances between lens elements and otherdimensional and optical details are enumerated and identified asfollows, namely that fe=the focal length for the e-line,

A=the aperture,

P=the Seidel coefficient for the Petzval sum, 1`=the Seidel coeflcientfor the astigmatism. Be=the magnification for the e-line, r=radius, lLo=distance of the Object, Lb=distance between the last lens and theimage, L=distance between two lenses,

d=thickness of lens,

nd=refractive index and Abbe number, do=thickness of cover glass.

The examples set forth in the descriptions of the several figures in thedrawing as hereinafter set forth, show that the correction meansprovided in accordance with the invention result in objectives in whichthe image eld curvature is satisfactorily leveled with very littleastigmatism. Fine correction which may be required later on does notmaterially affect the advantages of the invention.

Fig. l illustrates a lens system according to the invention in which theseveral lens elements shown in the drawing are characterized by thefollowing values:

Fig. 2 illustrates a lens system according to the invention in which theseveral lens elements shown in the drawing are characterized by thefollowing values:

4 shown in the drawing are characterized by the following values:

Fig. 4 illustrates a lens system according to the invention in which theseveral lens elements shown in the drawing are characterized by thefollowing values:

Fig. 5 illustrates a lens system according to The invention is notlimited to the exact values set forth in the foregoing specification orin the appended claims. It is known in this art that changes in a statedvalue may be made and compensated for by a corresponding change inanother related value. I claim therefore all such changes andmodifications as come within the principle of the invention and thescope of the appended claims.

We claim:

1. A microscope objective comprising a thick meniscus front lens, aplurality of converging lenses on the image side of said thick meniscus,lens elements for correcting the astigmatism caused by said thickmeniscus consisting of a dispersing cemented surface in one of saidconverging lenses and a single negative lens positioned on the imageside of said one converging lens near the rear end of said objective,said cemented surface being concave towards said thick meniscus, thecurvature of said cemented surface being such that it receives theoblique principal light rays under a large angle of incidence, saidfront lens being the only thick meniscus in the said objective.

2. A microscope objective including a thick the invention in which theseveral lens elements meniscus positioned as the front lens and having adispersing cemented surface within a converging lens element and anegative lens on the image side of said surface positioned behind thesaid meniscus whereby to correct for the astigmatism caused by saidthick meniscus, said dispersing cemented surface having the center ofits curvature on the object side of said objective, characterized by thefollowing data f=the focal length for the e-line,

A=the aperture,

2P=the Seidel coeiiicient for the Petzval sum, 2I=the Seidel coefficientfor astigmatism, B=the magnification for the e-line, r=radiusL5=distance o1' the object,

Ln=distance to the image,

L=distance between two lenses. d=thickness of lens,

na=refractive index and Abbe number.

3. A microscope objective including a thick meniscus positioned as thefront lens and having a dispersing cemented surface within a converginglens element and a negative lens on the image side of said surfacepositioned behind the said meniscus whereby to correct for theastigmatism caused by said thick meniscus, said dispersing cementedsurface having the center of its curvature on the object side of saidobjective, characterized by the following data wherein fe=the focallength for the e-line, A=the aperture, 2P=the Seidel coeiiicient for thePetzval sum, z1`=the Seidel coefiicient for astigmatism, B=themagnification for the e-line, r=radius Lo=distance of the object,Lb=distance to the image. L=distance between two lenses, d=thickness oflens,

:refractive index' and Abbe number.

4. A microscope objective including a thick meniscus positioned as thefront lens and having a dispersing cemented surface within a converginglens element and a negative lens on the image side of said surfacepositioned behind the said meniscus whereby to correct for theastigmatism caused by said thick meniscus, said dispersing cementedsurface having the center.. of its curvature on the object side of saidobjective, characterized by the following data d=0. 17 m=1. 5228/58. 5 l4 Lago, 6551s di=a. 15 1. 5228/56. 9 fl 2. 42

dwz. 15 1. 4339/95. 2 s, sa

d.=1. 0 1. 7276/28. 4 =ao. a7

Li=21. o rg =+3. 05

d5= 2.0 1. 6228/5-9 -se. o5

L4= 9.0 r|u=+12 0 d= 1.5 1. e700/41.2 r11=+ 8 02 -32 845s 2P: 0. o23 f.=+4. 419s zr=+o. 007 A= 0. 65

wherein f=the focal length for the e-line.

A=the aperture,

2P=the Seidel coefficient for the Petzval sum. 2I=the Seidel coefficientfor astigmatism, B=the magnification for the e-line, r=radiusL0=distance of the object,

Lb=distance to the image,

L=distance between two lenses, d=thickness of lens,

na=refractive index and Abbe number.

5. A microscope objective including a thick meniscus positioned as thefront lens and having a dispersing cemented surface within a converginglens element and a negative lens on the image side of said surfacepositioned behind the said meniscus whereby to correct for theastigmatism caused by said thick meniscus, said dispersing cementedsurface having the center of its curvature on the object side oi.' saidobjective, characterized by the following data wherein f=the iocallength for the e-line,

" A=the aperture,

2P=the Seidel coefcient for the Petzval sum, 21`=the Seidel coefficientfor astigmatism, B=the magnification for the e-line,

r=radlus Lo=distance of the object.

Ls=distance to the image.

L=distance between two lenses,

d=thickness of lens,

na=rciractive index and Abbe number.

6. A microscope objective including a thick meniscus positioned as thefront lens and having a dispersing cemented surface within a converginglens element and a negative lens on the image side of said surfacepositioned behind the said meniscus whereby to correct for theastigmatism caused by said thick meniscus, said dispersing cementedsurface having the center of its curvature on the object side ot saidobjective, characterized by the following data f=the focal length forthe e-line,

A=the aperture,'

2P =the Seidel coemcient for the Petzval sum, 2I'=the Seidel coeillcientfor astigmatism, B=the magnification for the e-line. r=radiusLo=distance of the object.

Lb=distance to the image,

L=distance between two lenses, 1 -.thickness of lens,

nd=refractive index and Abbe number.

GO'I'I'FRIED RAVIZZA.

' f KARL- KEINER.

WALTER KLEIN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,578,259 Boegehold Mar. 30, 1926 1,761,441 Foster June 3,1930 1,910,115 Luboshez May 23, 1933 2,050,024 Sonnefeld Aug. 4, 19362,206,155 Boegehold July 2, 1940

